The present invention, which is a continuation-in-part application of U.S. Ser. No. 637,217 filed July 17, 1984, relates to a thermocouple array for a thermal fluxmeter, namely to a device for measuring a thermal flux resulting from a temperature gradient and more particularly to a thermal fluxmeter having in its array several tens and preferably several hundreds or thousands of elementary thermocouples connected in series.
In the European Pat. No. 0 030 499 granted to the assignee of the present application on Aug. 8, 1984 and to which corresponds U.S. Pat. No. 4,382,154 issued to Thery et al on May 3, 1983, a thermal fluxmeter is described (more particularly with reference to FIGS. 3, 4 and 5 of these European and U.S. patents), said fluxmeter comprising, along a meandering path (FIG. 3), a succession of elementary thermocouples connected in series (FIGS. 4 and 5); this fluxmeter includes a plate made of a plastics material coated with a thin meandering layer or strip of a first conducting or semi-conducting substance, such as the alloy named constantan, this thin strip or layer being itself coated with a succession of zones, separated from each other, of an electrolytic thinner deposit of a second conducting or semi-conducting material, such as copper, having a thermoelectric power different from that of the first conducting or semi-conducting material. In the embodiment shown in FIG. 4 of these patents, said zone had a dissymmetrical form (dove-tail shape of the zone), whereas in the embodiment shown in FIG. 5 of both these European and U.S. patents the device comprised a succession of resin coatings each overlapping a portion of said zones and an adjacent portion of the strip or layer not coated with the deposit of said second material, thus providing again a dissymmetry. The elementary cells or thermocouples were connected in series by the strip or layer of the first material, which was continuous. It is the dissymmetry in the transverse direction which allowed an electromotive force to be generated in the series assembly of thermocouples, said electromotive force depending on the temperature difference to which each elementary cell was subjected, as the first and second above mentioned materials had different thermoelectric properties.
Furthermore, a thermal fluxmeter is known from the U.S. Pat. No. 4,197,738 issued to Monsieur Degenne on Apr. 15, 1980. This thermal fluxmeter is formed by series connected thermocouples and comprises a relatively thick plate made from an insulating material pierced with two series of transverse channels passing through the whole thickness of the plate; on each face of this plate is disposed a series of layers of a first conducting material separated from each other by narrow strips of the plate not coated with this first conducting material; furthermore, the channels are coated along their whole surface, the channels of the first series being coated with said first conducting material, whereas the channels of the second series are coated with a second conducting material, said two materials having different thermoelectric powers; finally, rings of the second conducting material surround the upper and lower edges of the channels of the second series of channels. The first material may be copper and the second material nickel. It will be noted that neither the coated layers of the first conducting material nor the coated layers of the second conducting material are continuous, but form an assembly of discontinuous surfaces (on the faces of the plate and on the inner periphery of the channels).
On the other hand, U.S. Pat. No. 4,029,521 issued to Korn et al on June 14, 1977 describes a thermoelectric detector comprising an inner support, a continuous strip of a first material, having a meandering shape, and a succession of discrete deposits of a second material disposed on this strip, the thermoelectric powers of these two materials being different; hot and cold zones are formed by using reflecting elements E, radiation absorbing elements G and conducting elements F forming a heat sink, these elements E, G and F creating hot and cold zones at the ends of the discrete deposits B disposed on a continuous strip A. No channel is provided through the deposits B and/or the strip A.
Finally two other U.S. Pats., i.e. No. 4,363,927 issued Dec. 14, 1982 to Wilson and No. 3,267,727 issued Aug. 23, 1966 to Benzinger, also disclose thermoelectric generators having a meandering structure.
Contrary to the prior techniques, the present invention relates to a thermal fluxmeter with a great number of thermocouples, comprising, on an insulating substrate, at least one thin continuous layer of a first conducting or semi-conducting material coated on at least one of its faces with a succession of zones, separated from each other and formed by thinner deposits of a second conducting or semi-conducting material having a thermoelectric power different from that of said first material, characterized by the fact that respective channels pass right through at least part of at least most of said zones and through the thin continuous layer, underlying said zones, without interrupting the continuity of said thin layer, these channels being offset in the same direction with respect to the center of each zone passed through.
Preferably, said channels are coated internally with a deposit of the second material.
Advantageously, said thin continuous layer is in the shape of a strip which is preferably meandering, being bent so as to form a rectangular or square structure.
In a first embodiment, the thin continuous layer is deposited on a substrate of an insulating material and it is coated on one face only, namely the one opposite the face fixed to the substrate, with thinner deposit zones.
In a second embodiment, the thin layer is coated on both faces with thinner deposit zones, the zones of one of the faces partially overlapping the zones of the other face on each side of the thin layer and each channel, which passes not only through the thin layer, but also through the overlapping portions of the two thinner deposits on each side of the thin layer, is offset with respect to the center of each of the two deposits in opposite directions above and below the layer.
Advantageously, the succession of the deposit zones and the portion not covered (by such zones) of the thin continuous layer or of the coated face or faces is coated with resin layers.
Each channel may open either within a deposit zone, or astride such a zone and a non-coated portion of the thin layer.
In another type of embodiment, the assembly of the thin continuous layer and of the zones deposited on one or both sides of said thin continuous layer is placed between two cover plates of an insulating material, notches being made in said zones so as to be surrounded along most of their sides by the respective deposit and each of said notches being extended by one of said channels traversing said thin continuous layer, said notches and channels being offset relatively to the center of the zones on one face of said thin continuous layer in a same direction along the longitudinal direction, although possibly meandrous, of said layer.
Advantageously the external surface of each cover plate, which is not in contact with said zones, is covered with a coating of a heat conducting material.
In a specific embodiment of this type there are two thin continuous strips located against opposite faces of a central plate of an insulating material, each thin continuous strip having said zones on the face thereof which is not in contact with said central plate.
Preferably, in this specific embodiment, the notches and channels corresponding to one thin continuous layer are offset in a first direction relatively to the longitudinal elongation (possibly in a meander) of the layer, whereas the notches and channels corresponding to the other thin continuous layer are offset in a second direction relatively to said longitudinal elongation, said second direction being opposite to said first direction.
The thermal fluxmeter of the invention may comprise several hundred elementary thermocouples, namely as many as there are zones on a face or each of the faces of the thin continuous layer.
Preferably the first material is the alloy constantan and the second material copper.
It will be noted that a device in accordance with the invention is distinguished essentially from the thermal fluxmeters described in European Pat. No. 0,030,499 and U.S. Pat. Nos. 4,382,154 and 4,029,521 by the presence of channels or notches, not provided in these previous patents, and from the fluxmeter described in U.S. Pat. No. 4,197,738 by the fact that the thin layer is continuous, whereas in this last U.S. patent none of the upper or lower coatings is continuous.